[Omin]

1,000,000,000ng is 1kg, so that'd would be as much plastic as solvent by mass.

[mda]

1,000,000,000ng = 1g

[gattr]

@Omin, @mda, just a side note: I recommend using the (centuries old, I guess) established typography rule and putting a space between the number and the unit symbol. See [1] for additional info.

[1] SI Unit rules and style conventions, https://physics.nist.gov/cuu/Units/checklist.html